Germany currently generates over 35 per cent of its electricity from solar and wind energy sources. To produce all this renewable energy more than 30,000 wind turbines have been constructed and roughly 1.7 million solar power installations have taken place, with installed capacities of 60 gigawatts and 46 gigawatts respectively.
These are very impressive numbers however, during the majority of the year only a small amount of this installed capacity is actually generated. In addition to this, on days which do not favour the renewable sources almost no electricity is generated from wind or solar. This means that taking both the good and the bad days into consideration the average total output of wind and solar energy is only around 17 per cent of the actual installed capacity.
Therefore, wind and solar power alone are not a reliable or stable electricity supply and alternatives are needed to fill the energy shortage between the electricity demand and how much electricity can be produced from wind and solar. Alternatives such as energy reserves or backup sources of electricity can be used to fill these gaps.
The more a nation relies on wind and solar energy then the greater the backup capacity it then requires. For example, on occasions where there is very little wind or solar energy, the backup power would be required to provide 100 per cent of the electricity that is demanded in that country which means it will have to store and/or produce large amounts of electricity.
Other alternatives are to have the country mainly rely on a source of power which produces a reliable and stable flow of electricity and then use wind and solar power to supplement the electricity. However, this will not help a country achieve its net zero goals.
In theory, the best option here is to have a backup energy storage system which stores any surplus energy that is produced on days where it is very sunny or very windy so that on occasions which do not favour wind or solar energy the electricity can be accessed from the storage system to power the nation. However, the issue with this is that electricity is very expensive and difficult to store in such large amounts.
At this moment in time, the most efficient way in storing the excess electricity is to use it to pump water into a reservoir against gravity. Then, when more electricity is needed the water flows down via a turbine generator and produces electricity on demand. Doing this leads to a total loss of energy of 25 per cent. However, the cost of building such plants along with the operation of them will add to the cost the consumer pays for their electricity and the plants will take up large areas of land which could potentially be used for something else.
In Germany there is already an example of the pump storage plants not being an economically viable solution to the problem. This came through a study in 2014 by the Bavarian Ministry of Energy. Instead it is more economically feasible to make use of existing reservoirs located in Sweden and Norway. They can be easily expanded and constructed at much lower costs than building entire new reservoir systems in Germany.
This comes with its own problems though as it requires the transportation of energy from Germany to Norway or Sweden which would mean high voltage lines and cables need to be built between the nations.
Therefore, at this current moment in time there is not an efficient way to store or use the excess energy from the renewable sources in Germany. This challenge will have to be passed before the nation can rely entirely on renewable energy.